1. Field of the Invention
The invention relates to a machine and method for bunching plant stems and to a gripper for such a machine. More particularly, the invention relates to a machine according to the introductory portion of claim 1.
2. Background Art
Dutch patent No. 1009091 discloses a machine for gathering plant stems into bunches. This machine utilizes a pair of rollers and a flexible band. Plant stems are natural products that do not allow of reproducibly rigid mechanical handling. The flexible band makes it possible for the plant stems to be received flexibly. The flexible band forms a loop, whose ends pass between the rollers, so that the loop projects on one side of the pair of rollers. In use, the plant stems are gathered in this loop. The plant stems are introduced between the rollers, after which a rotary movement of the rollers carries along the plant stems, clamped between the rollers, and presses them into the loop.
The ends of the band are pulled with a spring, so that the amount of band in the loop that projects outside rollers is not greater than is necessary to embrace the plant stems. Thus, the gathered stems are enclosed by the loop and also pulled against the rollers. As a result, the stems cannot fall out of the loop. When sufficient stems have been gathered, the rollers are moved apart, while the parts of the band that pass between the rollers move apart along with the rollers. As a result, the loop open sand the bunched stems can be taken out.
If the bunch is to be prevented from falling apart again when being taken out, it is desirable to tie the plant stems together before the loop opens. In that case, however, the rollers against which the bunch is pulled by the band are in the way, or at least the rotary shafts of the rollers are in the way. Thus, without transfer, it is difficult, if possible at all, to tie the bunch together. Transfer entails the risk of the stems in the bunch shifting relative to each other.